1. Field of the Invention
The present invention relates to a moisture sealing apparatus for a powdery flux for metal brazing, in particular, a powdery flux used in brazing of aluminum, copper or the like and having deliquescence, and more specifically to a moisture sealing apparatus for a powdery flux, which is useful upon applying the flux to a filler rod by means of an automatic mechanism.
2. Description of the Related Art
Chloride fluxes are used in metal brazing, in particular, brazing of aluminum. As the chloride fluxes, zinc chloride, sodium chloride, lithium chloride and potassium chloride are generally used either singly or in any combination thereof. These chloride fluxes are in the form of powder. Therefore, the tip of a filler rod is wetted with water or an aqueous mixture with a suitable binder added to water before use of a powdery flux so as to apply the flux thereto, thereby conducting brazing. However, since these chlorides all show strong deliquescence, a flux comprising, as a main component, any one of these chlorides absorbs moisture in the air and is wetted by the moisture when it is allowed to stand in the air. Accordingly, the flux aggregates into a number of small lumps whenever the filler rod dipped into the liquid is inserted into the flux, so that the flux becomes crumbly and difficult to adhere to the filler rod. Before long, the flux deliquesces and becomes soft and sticky, leading to an utter impossibility of its use.
The present inventor previously proposed a container for preventing the moisture absorption of these deliquescent fluxes (Japanese Patent Application Laid-Open No. 126666/1988). This container is such that an air box is provided under a container for containing a powdery flux therein through a screen, and this air box is connected to a source of dry air supply.
However, in the above-described flux container, dry air is blown into the container through a very fine-mesh screen from under the powdery flux. Therefore, the meshes of the screen are partly clogged with the flux when the flux is used for long time, so that the passage of the air becomes deflected. The flux situated at portions where the passage of the air has become ill is hence not satisfactorily dried, and is wetted to aggregate into lumps. As a result, a vicious circle that the passage of the air is increasingly prevented arises. Accordingly, there has been a disadvantage that it requires time and labor in that the occurrence of clogging of the screen must be always monitored to clean the screen.
In addition, when the flux contained in the container decreases, partial blow-by of the air arises, which makes it impossible to evenly introduce dry air. Therefore, the amount of the flux contained in the container has also had to be monitored.